Fluidic devices, such as including a network of fluid-filled or fluid-carrying regions, can be used for a variety of applications, such as for chemical analysis or assay. Such devices can be fabricated to support analysis using analyte or reagent volumes on the order of microliters, nanoliters, picoliters, or smaller volumes, for example. Such miniaturized devices carrying such minute volumes can be referred to as “microfluidic” devices. Microfluidic devices can be fabricated using lithographic techniques, such as to form integrated fluidic networks or analysis systems, in a manner similar to integrated circuit fabrication.
In one approach, such devices can include valve structures comprising microelectromechanical (MEMS) structures, such as to control flow along a branch or channel of a fluidic device. However, as the complexity of analysis or assay increases, increasing numbers of valves and related control devices can inordinately increase cost and size, decrease reliability, or thwart objectives such as disposability or rapid replacement. Thus, controlling flow in such fluidic devices exclusively using “active” valve structures such as MEMS structures can be prohibitively expensive or can limit an overall complexity of a fluidic device. Such limitations can become significant where the fluidic device is to be used in a point-of-care diagnostic or other application where portability, low cost, or disposability is desired.
In some approaches, flow in a fluidic device can be controlled using one or more passive fluidic networks included as a portion of the fluidic device. Easley et al., International Patent Application Publication Number WO 2007/024829 A2, titled “Passive Components for Micro-Fluidic Flow Profile Shaping and Related Method Thereof” mentions (at page 6) “passive flow control components . . . presented as analogs to circuit components in the electronic arts, and thus can be combined in a similar manner. The passive flow components of the present invention include fluidic diodes, fluidic capacitors, and fluidic inductors.” Easley et al. is hereby incorporated herein by reference in its entirety, including Easley et al.'s description of passive flow control components for use in a fluidic device, such as a microfluidic device.